Liquid fuel pumping apparatus



P 1969 M. G. MOWLE 3,465,678

LIQUID FUEL PUMPING APPARATUS Filed Oct. 10, 1967 2 Sheets-Sheet lNVENTOR J/M 41:? jaw! m, ALMA A TORNEYS Sept. 9, 1969 M G. MOWLE LIQUIDFUEL PUMPING APPARATUS 2 Shets-Sheet 2 Filed Oct. 10, 1967 2 lNVE OR EBY ' ATTO United States Patent 3,465,678 LIQUID FUEL PUMPING APPARATUSMichael George Mowle, Kenton, England, assignor to C.A.V. Limited,London, England Filed Oct. 10, 1967, Ser. No. 674,230 Claims priority,application Great Britain, Oct. 21, 1966, 47,246/ 66 Int. Cl. F04b13/02, 49/00 US. Cl. 1032 Claims ABSTRACT OF THE DISCLOSURE Thisinvention relates to liquid fuel pumping apparatus for supplying fuel tointernal combustion engines and has for its object to provide such anapparatus in a simple and convenient form.

A liquid fuel pumping apparatus in accordance with the inventioncomprises in combination, an injection pump arranged to be driven intimed relationship with the engine with which the apparatus isassociated, the injection pump being arranged to deliver fuel to anoutlet port during an injection stroke thereof, a one way valve disposedintermediate the injection pump and said port, said valve being arrangedto be closed after the delivery of fuel to the port has ceased, andmeans for relieving the pressure on the opposite sides of said valveafter injection has ceased, to a pressure or pressures below thepressure which is attained during an injection stroke of the injectionpump.

in the accompanying drawings:

FIGURE 1 is a sectional side elevation of one example of a liquid fuelpumping apparatus in accordance with the invention, and

FIGURE 2 is a section through the apparatus of FIG- URE 1.

The apparatus comprises a body part 10 in which is mounted a rotarycylindrical distributor 11 which is adapted to be driven in timedrelationship with an engine with which the apparatus is associated. Atone end of the distributor member there is provided a transverse bore 12in which is mounted a pair of pumping plungers 13 which are arranged tobe moved inwardly as the distributor member rotates by means of anannular cam 14 surrounding the distributor member at this point. Forthis purpose, the annular cam is provided with a plurality of inwardlyextending and diametrically disposed pairs of cam lobes which arearranged to be contacted by rollers which are mounted at the outer endsof the pumping plungers respectively.

At the opposite end of the distributor member is mounted the rotary partof a vane-type fuel feed pump 16 which is provided with an inlet and anoutlet in the body part. The outlet is in communication with an axiallydisposed feed passage formed within the body part and the inlet is incommunication with an inlet port formed on the exterior of the bodypart. The inlet port in use, is arranged to be connected to a source ofliquid fuel. Moreover, the inlet and outlet of the fuel feed pump areinterconnected by a relief valve (not shown) which is so arranged thatice the outlet pressure of the feed pump varies in accordance with thespeed at which the distributor member is driven.

Formed in the distributor member is a stepped axial passage 17 which atone end is in communication with the transverse bore 12. At its otherend the passage is closed by a plug 18 and furthermore this end of thepassage is enlarged. From the enlarged end of the passage extends aradially disposed delivery port 19 which is arranged to register in turnand as the distributor member rotates, with a plurality ofequi-angularly spaced delivery passages 20 formed in the body part. Thedelivery passages in use, are connected respectievly to the injectionnozzles of the associated engine. The registration of the delivery port19 with one of the delivery passages 20 is arranged to occur before theplungers are moved inwardly by the cam lobes and for a period after theplungers have moved inwardly to their maximum extent.

The stepped axial passage 17 accommodates a cylindrical valve member 21which is urged in a direction away from the enlarged end of the passage,by means of a coiled compression spring 22 which is located in saidenlarged end. The extent of movement of the valve member under theaction of its spring is limited by a step 23 defined in the periphery ofthe axial passage. The valve member is provided with a blind bore whichextends from its end which is directed towards the transverse bore 12and this blind bore is provided with a transverse drilling which breaksout onto the periphery of the valve member. When the valve member is incontact With the step 23, the transverse drilling is in communicationwith a groove 24 formed in the periphery of the axial passage at thispoint. Moreover, the groove is in communication with a plurality ofequi-angularly spaced and radially extending inlet ports 25 formed inthe distributor member, and which are arranged to register in turn andas the distributor rotates with an inlet port 26 formed in the bodypart. The axial position of the transverse drilling in the valve memberis so chosen that during the initial inward movement of the pumpplungers 13, the cylindrical valve member 21 will be moved axiallyagainst the action of its spring thereby to displace fuel from theenlarged end of the axial passage through the delivery port 19, andsubsequently the transverse drilling will be exposed to the enlarged endof the axial passage so that further flow of fuel from the transversebore takes place by way of the blind bore formed in the valve member andthe transverse drilling.

The inlet port is in communication with the feed passage 15 formed inthe body part by way of a groove on the distributor member and athrottle valve 27 is provided to control the rate at which fuel can flowthrough the inlet port. The throttle valve is movable angularly by agovernor (not shown) which is responsive to the speed at which thedistributor member is driven and an operator adjustable member isprovided to control the setting of the governor. The throttle member hasa groove formed in its periphery, the degree of exposure of which to aport in the wall of the body part determines the quantity of fuel whichpasses to the inlet port.

The operation of the apparatus thus far described will now be explainedassuming that the delivery port 19 has just opened to one of thedelivery passages 20 and the pumping plungers 13 are just starting tomove inwardly under the influence of the cam lobes. Initially, the valvemember 21 is moved axially against the action of its spring by the fuelwhich is being driven from the transverse bore 12 by the plungers. Theaxial movement of the valve member displaces fuel from the enlarged endof the axial passage through the delivery port to the delivery passagewhich is in register therewith and to the appropriate injection nozzleof the engine. It should he mentioned that during this movement theinlet passages 25 are out of register with the inlet port 26. Continuedaxial movement of the valve member places the transverse drillingthereof in communication with the enlarged end of the axial passage andthe remainder of the fuel which is to be displaced from the transversebore passes by way of the blind bore in the valve member and thetransverse drilling to the enlarged end of the axial passage. When therollers reach the crests of the cam lobes no further inward movement ofthe pumping plungers takes place and consequently the supply of fuel tothe engine ceases. As the rollers roll over the crests of the cam lobes,the plungers move outwardly and the valve member under the action of thespring 22 and the fuel flowing to the transverse bore, is moved in thereverse direction to the closed position. By this means a predeterminedamount of relief of the pressure in the enlarged end of the axialpassage occurs. The cam lobes are shaped to provide a period of dwell inthe outward movement of the plungers so that such further outwardmovement is temporarily halted. However, the amount of outward movementpermitted to the plungers is always sufiicient to ensure that thetransverse drilling in the valve member is brought back into registerwith the groove formed in the axial passage and which is incommunication with the inlet passages. Subsequently, the delivery port19 moves out of register with the delivery passage 20 and before thisoccurs one of the inlet passages is brought into register with the inletport 26.

In order to ensure that the valve member 21 seats against the step 23and in order to stabilise the pressure existing in the transverse bore12 and the portion of the axial passage 17 downstream of the valvemember, together with the bore in the valve member and the groove,Whilst the plungers are temporarily halted, it is arranged that thesevolumes are placed in communication with a low pressure. Conveniently,this low pressure is the pressure pertaining in the space surroundingthe annular cam, and this space is normally in communication with adrain port provided on the external surface of the apparatus. In orderto achieve this, drain passages are provided in the body part of thepump and for registration in turn with a plurality of axially extendingdrain grooves 31 formed in the periphery of the distributor member. Thedrain grooves are respectively in communication with the inlet passages25, and the registration of the drain grooves with the drain passages isarranged to occur at the same time as the inlet port 26 registers withone of the inlet passages 25. Moreover, the drain grooves move out ofcommunication with the drain passages before the delivery port moves outof communication with one of the delivery passages. During the time thatthe drain grooves are open to the drain passages, fuel flows by way ofthe inlet port to drain, but nevertheless, the pressure in the aforesaidvolumes is stabilised to drain pressure and this stabilisation occurswhilst the plungers are held against outward movement by the dwellperiod of the cam lobes. High pressure in the enlarged end of the axialpassage 17 ensures that at this point of operation the valve member 21assisted by the spring is moved into contact with the step 23. As soonas the aforesaid dwell period is over and when the drain grooves havemoved out of register with the drain passages, fuel flows to thetransverse bore 12 to move the plungers outwardly, the amount of fuelbeing controlled by the setting of the throttle.

In order to ensure that the pressure in the enlarged end of the axialpassage after the delivery port has closed, and during the fillingperiod, is always at a predictable and relatively low pressure, theenlarged end of the axial passage is arranged to be placed incommunication with the outlet of the feed pump. For this purposeextending from the enlarged end of the axial passage are a plurality ofradially extending and equiangularly spaced dump ports 32 which arearranged to register with a dump passage 33 in communication with thefeed passage 15, whilst the delivery port 19 is out of register with adelivery passage 20.

By the arrangements described, the high pressures which exist at the endof the injection period in conventional pumps of this type and whichhave a tendency to cause irregularities within the pump now no longerexist.

In order to be able to shape the delivery curve of the fuel output ofthe apparatus with respect to the speed at which the apparatus isdriven, an adjustable quantity of fuel is allowed to escape from theenlarged end of the axial passage at the commencement of the inwardmovement of the pumping plungers. For this purpose there is provided inthe body part a cylindrical chamber 40 in which is mounted a shuttle 41which is loaded towards one end of the chamber by means of a coiledcompression spring 42 located at the other end of the chamber. Theextent of movement of the shuttle towards said other end of the chamberis limited by an adjustable stop 43 which can be adjusted from theexterior of the body part of the apparatus. Said one end of the chamber40 is brought into communication with the enlarged end of the axialpassage at the same time as the delivery port 19 is brought intoregister with one of the delivery passages 20. For this purpose a spillpassage 44 is provided in the body part and which is in communicationwith said one end of the cylinder. The other end of the spill passage ispositioned so that it registers with one of the aforesaid dump ports 32at the appropriate time. By this means the initial quantity of fuelwhich is delivered through the axial passage 17 when the plungers aremoved inwardly flows to said one end of the chamber and the shuttletherein is moved against the action of its spring into contact with theadjustable stop 43, When the movement of the shuttle is halted by thestop, injection of fuel to the engine proceeds as described previously.The other end of the chamber which contains the shuttle 41 is incommunication with the inlet of the feed pump by way of a passage 45 andconsequently fuel is displaced to the inlet of the feed pump when theshuttle is moved against the action of its spring. The period ofregistration of the spill passage with one of the dump ports occurs foronly a portion of the time during which the delivery port is open to adelivery passage. When the delivery port has closed and whilst one ofthe dump ports 32 is in communication with the dump passage 33 it isarranged that fuel can flow from said one end of the chamber into theenlarged end of the axial passage and for this purpose a return passage46 is provided which is in communication with said one end of thechamber 40. This return passage communicates with one of the dump ports32 at the appropriate time and the shuttle moves under the action of itsspring towards said one end of the chamber.

The extent of movement of the shuttle towards said one end of thechamber is controlled by a stop, the setting of which depends upon thespeed at which the apparatus is driven. The stop comprises a fluidpressure operable piston 47 which is spring loaded in one direction andwhich is urged in opposition to the loading of its spring by fuel underpressure from the outlet of the feed pump. The shuttle 41 is providedwith a transverse drilling through which the valve member extends and anabutment is provided in the drilling 48 which co-operates with a camsurface formed on the periphery of the piston 47 remote from said oneend of the chamber. The cam surface is shaped in any convenient mannerso that the extent of movement of the shuttle 41 towards said one end ofthe chamber under the action of its springs is limited. By shaping thecam surface any desired fuel output curve can be attained.

The variation in the timing of injection of fuel to the engine can beobtained in the usual manner with this type of pump by varying theangular setting of the an- 1 nular cam within the body part. For thispurpose a fluid pressure operable piston may be provided which iscoupled to the annular cam, the piston being resiliently loaded in onedirection and movable in the opposite direction by fuel under pressurederived from the outlet of the feed pump.

Having thus described my invention what I claim as new and desire tosecure by Letters Patent is:

1. A liquid fuel pumping apparatus for supplying liquid fuel to aninternal combustion engine and comprising in combination, an injectionpump arranged to be driven in timed relationship with the engine withwhich the apparatus is associated, the injection pump being arranged todeliver fuel to an outlet port during an injection stroke thereof, a oneway valve disposed intermediate the injection pump and said port, saidvalve being arranged to be closed after the delivery of fuel to the porthas ceased, means for relieving the pressure on the opposite sides ofsaid valve after injection has ceased, to a pressure or pressures belowthe pressure which is attained during an injection stroke of theinjection pump, and a rotary valve adapted to be driven in timedrelationship with the injection pump, said rotary valve serving tocontrol communication between the upstream side of said valve and saidoutlet port, the means for relieving the pressure upstream of the valvebeing inoperative until said rotary valve has closed.

2. A liquid fuel pumping apparatus as claimed in claim 1 in which saidone way valve during its movement towards the closed position, allows apredetermined volume of fuel to be displaced from the upstream sidethereof, the means for relieving the pressure downstream of the valvebeing operative before said rotary valve has closed.

3. A liquid fuel pumping apparatus as claimed in claim 2 in which aplurality of said outlet ports are provided equal in number to thenumber of cylinders of the engine to which fuel is to be supplied, saidrotary valve having a delivery port in communication with the upstreamside of said one way valve, the delivery port registering in turn, andduring successive injection strokes of the injection pump with passagescommunicating respectively with said outlets, the means for relievingpressure upstream of the one way valve comprising a plurality of dumpports formed in the rotary valve and which register in turn, with a dumppassage thereby to relieve the pressure upstream of the one way valveafter the delivery passage has moved out of register with a deliveryort. p 4. A liquid fuel pumping apparatus as claimed in claim 3 in whichthe means for relieving pressure downstream of the one way valvecomprises a plurality of ports formed in the rotary valve which arebrought into register with a spill passage before the delivery port hasclosed to a delivery passage.

5. A liquid fuel pumping apparatus as claimed in claim 4 in which fuelis supplied to the downstream side of the one way valve during thefilling strokes of the injection pump from a source of fuel underpressure, throttle means being provided to control the quantity of fuelsupplied to the injection pump.

6. A liquid fuel pumping apparatus as claimed in claim 5 including ashuttle movable within a chamber, means biasing said shuttle towards oneend of the chamber, the rotary valve acting to place said one end of thechamber in communication with the upstream side of said valve during theinitial portion of the injection stroke of the injection pump, so that aquantity of fuel is displaced into said chamber, and a stop for limitingthe movement of the shuttle away from said end of the chamber theshuttle returning to said end of the chamber when said dump passages andports are brought into communication with each other.

7. A liquid fuel pumping apparatus as claimed in claim 6 including stopmeans for limiting the extent of movement of the shuttle towards saidend of the chamber.

8. A liquid fuel pumping apparatus as claimed in claim 7 in which thesetting of said stop means is dependent upon the speed at which theapparatus and the associated engine are driven.

9. A liquid fuel pumping apparatus as claimed in claim 8 including afeed pump for supplying fuel to the injection pump, valve means forcontrolling the output pressure of the feed pump so that the pressurevaries in accordance with the speed at which the apparatus is driven,said stop means comprising a fiuid pressure sensitive piston which issubjected to the output pressure of said feed pump.

10. A liquid fuel pumping apparatus as claimed in claim 9 in which theshuttle is biased towards said end of the chamber by a coiledcompression spring.

References Cited UNITED STATES PATENTS 3,006,281 10/1961 Delaney 10341 X3,331,327 7/1967 Roosa. 3,352,245 11/1967 Wolff l032 3,364,863 1/1968Olszewski et al.

DONLEY J. STOCKING, Primary Examiner W. I. KRAUSS, Assistant Examiner

